1. Technical Field
The present invention relates to a projector.
2. Related Art
There is a known projector if related art including a light source apparatus, a plurality of liquid crystal panels that separately modulate a plurality of color light fluxes outputted from the light source apparatus, a cross dichroic prism that combines the light fluxes modulated by the plurality of liquid crystal panels to form an image, and a projection optical apparatus that enlarges and projects the formed image on a projection surface, such as a screen. As a projector of this type, there is a known configuration in which the cross dichroic prism, which has light incident surfaces to which the plurality of liquid crystal panels described above are fixed, is integrated with the projection optical apparatus by using a support member.
There is a problem with the projection optical apparatus, which has a temperature characteristic in accordance with which the focus position is slightly changed when the temperature changes. To address the problem, there is a proposed projector in which an expandable and shrinkable member is disposed between the support member that supports the prism and a holding member that holds the projection optical apparatus (see JP-A-2010-256394, for example).
In the projector described in JP-A-2010-256394, when the amount of back focus (back focal length) of the projection optical apparatus decreases due, for example, to an increase in temperature, the expandable and shrinkable member expands or shrinks to move the liquid crystal panels and the cross dichroic prism described above in a direction in which they slightly approach the projection optical apparatus. The liquid crystal panels can thus be located in the back focus position of the projection optical apparatus irrespective of any change in temperature, whereby defocus can be avoided.
A projector includes in some cases a plurality of optical parts, such as a plurality of reflection mirrors that deflect the optical path of the light outputted from a light source apparatus and a light attenuator that blocks part of light incident thereon to adjust the amount of light used for image formation. In the thus configured projector, stray light that is not used for image formation tends to be produced. The stray light is likely to enter a projection optical apparatus.
On the other hand, the projection optical apparatus is in many cases formed of an assembled lens including a plurality of lenses and a lens barrel that accommodates the plurality of lenses therein. The lens barrel is in many cases made of a synthetic resin in consideration of manufacturability and light weight.
When light is incident on the lens barrel made of a synthetic resin, the lens barrel is heated and distorted due to thermal expansion in some cases. In such cases, the positions of the projection lenses disposed in the lens barrel slightly change, undesirably resulting in defocus of a projected image.